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Old 01-30-2010, 11:41 AM   #1
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Turning walls from 4" To 8"


House is 70 years old and I live in Indiana. I want to build new 4" walls over the existing exterior walls of my house. It would be great for the heating and cooling bills. I want to build these on the inside of the house and use drywall. (Currently has ugly paneling)

My questions are should I use faced or unfaced insulation? And should I knock holes between the existing studs, through the existing walls to allow for air flow between the new insulation and old. My worry is moisture build up between the new and old walls, it wouldn't be able to escape.

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Old 01-30-2010, 11:57 AM   #2
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Turning walls from 4" To 8"


If your house is 70 years old is there insulation in the existing wall cavities?
My house is only 55 years old & the Rvalue of the insulation is R2
I've replaced probably 75% of the insulation on my exterior walls
You are far better off taking the outside wall sheetrock down & put in new R15 insulation
Check the sheathing at the same time, updated any wiring that needs to be updated
Building a 2nd wall is really the wrong way to go

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Old 01-30-2010, 12:35 PM   #3
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Turning walls from 4" To 8"


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Originally Posted by Scuba_Dave View Post
Building a 2nd wall is really the wrong way to go
Huh?

actually building a second wall allows for a huge volume for insulation.

the one thing I would suggest is if the second wall is driectly next to the original wall, stagger the studs so you do not have effectively an 8" stud. There is a low r value for the wood compared to fiberglass or whatever and if you put them side by side, there is no room in between them for insulation.


I have a friend that has 1' (effective) thick walls using this method. It's 14 today (to let you know the weather in my area typically). He has a total electric house of about 1600 sq feet plus basement. His electric bill is less than $100/month. that includes lights, cooking, heating, water heat, general use, everything and no gas bill.


do you have some other method that would allow R30+ walls dave?
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Old 01-30-2010, 12:51 PM   #4
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Turning walls from 4" To 8"


It just screams of a hack job building another inside wall
If I saw a house like that when going to buy a house I'd pass, or seriously reduce my offer
Before I did that I'd rip the old walls down, update the electric, insulate with R15 & then add 1" rigid board to the inside
Then when the house is resided (eventually) add rigid board on the outside

I've yet to see any 70 year old house that would not benefit by pulling the old walls down, inspecting the exterior sheath, insulating & updating wire
If there are gaping holes (like my house had) around the old window framing then adding another wall will not have as much effect as redoing the exterior walls
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Old 01-30-2010, 01:40 PM   #5
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Turning walls from 4" To 8"


Quote:
Originally Posted by Scuba_Dave View Post
It just screams of a hack job building another inside wall
If I saw a house like that when going to buy a house I'd pass, or seriously reduce my offer
Before I did that I'd rip the old walls down, update the electric, insulate with R15 & then add 1" rigid board to the inside
Then when the house is resided (eventually) add rigid board on the outside

I've yet to see any 70 year old house that would not benefit by pulling the old walls down, inspecting the exterior sheath, insulating & updating wire
If there are gaping holes (like my house had) around the old window framing then adding another wall will not have as much effect as redoing the exterior walls
I'm not doubting the need to remove what ever sheathing is there and repairing and upgrading as needed. I have simply found no other way to have an R30+ value wall although closed cell spray foam would come closer than anything else. I wonder what a cost comparison between the two methods would show. The spray foam is just so dang expensive. If somebody could find a way to reduce the costs of that, it would become a more used product saving millions if not billions in heating and cooling costs in a very short time.


btw: those extra depth walls allow for some really useful built ins and if you do not get carried away, you do not reduce the overall benefit of the insulation too much.

they allow for a bench seat window at every window too!!
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Old 01-30-2010, 02:52 PM   #6
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Turning walls from 4" To 8"


I don't think the poster is going to remove the current paneling and the plaster underneath to insulate the entire two wall depth. He's going to build the wall in front and insulate that with fiberglass batts.
There are a few alternatives to improving the insulation without it looking like (as Scuba put it) "a hack job". He's not going to get R-30, but he never was. An complete house overview, including doors, windows and attic will provide a better result then doubling the walls.
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Old 01-30-2010, 08:14 PM   #7
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Turning walls from 4" To 8"


It's not meant to be a hack job in any way. I want thicker walls and at the same time I am also rewiring the entire house and upgrading to total electric with 200 amp service. That's a good point about it probably being bad idea to just go over it from a buyers standpoint. It would be smarter for me to just rip out the paneling and plaster then stagger the 2x4's.

So how does that sound to tear out the existing paneling/plaster, and insulation. Fix any holes in the exterior sheathing then fill the existing walls with unfaced r13 then stagger my 2x4's for the new wall and use faced R13 for the innermost part of the wall.

I'll also be insulating the attic better and the floors and replacing the doors. The windows are less than 10 years old. The goal is to get rid of a $600 gas bill every month during winter and make it cheaper to cool in the summer. At some point I also plan on taking down the existing siding and putting up a new layer of sheathing and house wrap, and possibly bricking the exterior.

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Old 01-31-2010, 09:31 AM   #8
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Turning walls from 4" To 8"


I would spend the money on a closed cell foam job instead of reducing room size and getting less insulating value with fiberglass batts. Why spend extra time and money on framing when the same results can be had in the structure you currently have?
Adding brick to a structure that didn't have it before will take a significant structural addition. The scenario will be dictated by how high the brick will go on the house.
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